CSV vs XLSX vs TXT: Which Format to Use?

You have data. You need to save it. But which alphabet soup extension do you choose? .csv, .xlsx, or .txt?

They all hold text and numbers, but they work very differently. Choosing the wrong one can lead to lost formatting, large file sizes, or compatibility nightmares.

The useful differences are structure, formatting, size, compatibility, and what each format preserves when saved.

The Contenders

1. CSV (Comma Separated Values)

Format: Plain text.
Structure: Rows separated by newlines, columns separated by commas.
Formatting: None (no bold, colors, formulas).
Compatibility: Universal. Opens in everything from Notepad to Excel to Python.

2. XLSX (Excel Workbook)

Format: Binary (actually a zipped XML structure).
Structure: Complex workbook with sheets, rows, columns.
Formatting: Rich (fonts, colors, borders, merged cells).
Features: Formulas, charts, macros, pivot tables.
Compatibility: Requires Excel, Google Sheets, or specific libraries.

3. TXT (Plain Text)

Format: Plain text.
Structure: Unstructured or loosely structured (e.g., tab-separated).
Formatting: None.
Compatibility: Universal.

Comparison Table

Feature	CSV	XLSX	TXT
File Size	Small	Medium/Large	Smallest
Formulas	No	Yes	No
Formatting	No	Yes	No
Multiple Sheets	No	Yes	No
Readability	High (Human & Machine)	Low (Machine only)	High
Speed	Fast to read/write	Slower	Fast
Max Rows	Unlimited	1,048,576	Unlimited

When to Use CSV

Use CSV when:

Moving data between systems: Exporting from a database to import into a CRM.
Programming: Python, R, and JavaScript love CSVs.
File size matters: You have millions of rows and don't need formatting.
Simplicity is key: You just need the raw data, nothing else.

Don't use CSV when:

You need to save formulas (=SUM(A1:A10) will just become the result or text).
You need multiple tabs/sheets in one file.
You need to highlight cells or change fonts.

When to Use XLSX

Use XLSX when:

Human analysis: You are working in Excel doing calculations, charts, and analysis.
Presentation: You need the data to look good (colors, borders).
Complex models: You have formulas linking different sheets.
Data validation: You use dropdowns and cell restrictions.

Don't use XLSX when:

You are feeding data to a script or program (libraries are slower/heavier).
You need to open the file in a simple text editor.
You have more than 1 million rows (Excel will cut them off).

When to Use TXT

Use TXT when:

Unstructured data: Logs, notes, readme files.
Custom delimiters: You are using Tab-Separated Values (TSV) or Pipe-Separated Values (|) to avoid comma issues.
Configuration files: Simple key-value pairs.

Don't use TXT when:

You have structured tabular data (CSV is better standard).
You need any kind of spreadsheet functionality.

Real-World Scenarios

Scenario 1: Sending a product catalog to a vendor.

Winner: CSV. It's the standard for e-commerce imports (Shopify, Amazon).

Scenario 2: Creating a monthly financial report for your boss.

Winner: XLSX. They want to see the totals calculated, formatted nicely, and maybe a chart.

Scenario 3: Saving server logs.

Winner: TXT (or .log). Just raw lines of text appended over time.

Scenario 4: Backing up a database table.

Winner: CSV (or SQL dump). Efficient and easy to restore.

Converting Between Formats

It's easy to switch:

Excel to CSV: File > Save As > CSV. Warning: You lose formatting and formulas.
CSV to Excel: Open in Excel > Save As > Excel Workbook.
CSV to TXT: Just rename the extension (technically works) or Save As > Tab delimited.

The Bottom Line

Data Transfer & Code: Go CSV.
Analysis & Presentation: Go XLSX.
Raw Text & Logs: Go TXT.

Choose the right tool for the job, and your data will thank you.

Need to convert formats? HappyCSV can help you transform and clean your data regardless of the format.